Signal translating apparatus



July 29, 1941.

F. GRAY ETAL 2,250,529

SIGNAL TRANSLATING APPARATUS Filed Feb. 11. 1939 MUL SIGNAL INDIVIDUALSIGML INDIVIDUAL SIGNAL INVENTORS! F GRAY J. B. JOHNSON BY ATTORNEYPatented July 29, 1941 SIGNAL TRANSLATING APPARATUS Frank Gray, NewYork, N. Y., and John B. J ohnson, Maplewood, N. J., assignors to BellTelephone Laboratories, Incorporated, New York, N. Y., a corporation ofNew York Application February 11, 1939, Serial No. 255,899

12 Claims. (01. 250-152) This invention relates to signal translatingapparatus and more particularly to electronic commutators for multiplextelephone systems such as disclosed in the applications of Frank Gray,

Serial No. 255,897 filed February 11, 1939, and

Serial No. 255,898, filed February 11, 1939.

One'object of this invention is to faithfully commutate a plurality ofcomplex signals such,

for example, as signals corresponding to speech and music.

Another object of this invention is to facilitate the accurateconversion of speech and music into electrical waves.

Still another object of this invention is to prevent electroniccross-talk and distortion in electronic commutators.

A further object of this invention is to improve and to simplify thestructure of electronic commutators.

In one illustrative embodiment of this invention, an electroniccommutator comprises a plurality of secondary electron emissive targets,a

. collector electrode in cooperative relation with the targets, andmeans for producing an electron beam whichimpinges upon the targets insequence and repeatedly at high frequency.

In accordance with one feature of this invention, the targets are madeof varying width, for example, sectoral or wedge-shaped, and means,

such as deflector plates, are provided in cooperathe beam deflectingplates for shielding the latter from one another.

In accordance with a further feature of this invention, the severaltargets are fabricated as a unitary structure. For example, in onespecific form, the targets may be spaced radial sections of a disc ofgood secondary electron emissive material. The portions of the discintermediate the targets may be treated or coated to prevent secondaryemission therefrom.

The invention and the foregoing and other features thereof will beunderstood more clearly and fully from the followingdetailed-description with reference to the accompanying drawing inwhich:

Fig. 1 is a perspective view of an electronic commutator illustrative ofone embodiment of this invention, portions of the enclosing vessel,

collector electrode, target electrode and shield electrode being brokenaway to show details of construction more clearly;

Fig. 2 is a sectional view along line 22 of Fig.-

1 showing the construction of the target electrode;

Figs. 3 and 4 are detail sectional views along lines 3-3 and 3-4,respectively, of Fig. 1,11- lustrating the form and association of theshield and deflecting electrodes; and

Fig. 5 is a circuit diagram illustrating one way of operating theelectronic commutator shown in Fi .1.

Referring now to the drawing, the electronic commutator disclosedtherein comprises an elongated, evacuated enclosing vessel lil havinginwardly extending coaxial stems II and. I2 at op-, posite ends, thestem H terminating in a press I3.

Supported by the stem Ii is an electron beam producing and deflectingstructure which may be of the construction disclosed in theaforementioned applications of Frank Gray. This structure comprises acathode, which may be of the equipotential indirectly heated type,including a heater filament I4 and a cup-shaped or cylindrical sleeve l5coated on its outer surface with an electron emissive coating. Thecathode is supported by leading-in conductors l6 embedded in the pressi3. It will be understood, of course, that although a heater typecathode has been shown, other types of cathodes, for example,filamentary, may be employed.

Immediately adjacent the cathode is a concentrating electrode includinga cylindrical portion ll coaxial with the sleeve l5, and end flanges l8and IS. The concentrating electrode may be supported by a plurality ofrods or uprights 2U afiixed to the flange I8 and carried by a pair ofbands or collars 2| clamped about the stem II. An insulating spacer ismounted on the concentrating electrode and comprises a tubular bodyportion 22 coaxial with the concentrating electrode, and end flanges 23and 24, the flange 23 being afiixed to the flange l9 as by rivets oreyelets 25.

An elongated tubular anode 26, of circular or other cross-section, isfitted in the bore in the body portion 22 of the insulating spacer andis provided with a flange or collar 21 seated upon the flange 24. Theanode 26 is coaxial with the concentrating electrode and preferablyprojects into the cylindrical portion I1 thereof as indicated in Fig. 5.The other end of the anode projects into the space bounded by deflectoror potential, thousand cycles per second, by oscillators 41through.transformers- 48, the. two oscillators. be- 7 ing '90 degreesout of .phase so that. the deflector tor sweep plates produce a rotatingfield. .As175 sweep plates 28 and 29 which are equally spaced from thelongitudinal axis of the anode. Each of the deflector or sweep plates,as shown in Fig. 1, comprises a rectangular portion and an outwardlyinclined trapezoidal portion, and is supported by a rigid rod or wire 30afiixed to and carried by the flange 24. Leading-in connection to thedeflector or sweep plates may be established through insulatedconductors 3| extending from the press I3.

The concentrating electrode l1, anode 25 and. sweep or deflector plates28 and 29 constitute an electron lens system which has a focal pointjust inside the end of the anode '26 opposite the cathode l andwhichproduces an image of this point on the targets to be describedhereinafter.

An annular target electrode 32 is supported coaxial with the anode 25 byleading-inconductors 33 sealed in the side of the stem [2. Thiselectrode may be a disc of a material, such as nickel or beryllium,having. goodsecondary electron emission properties, and, as shownclearly -in Fig. 2, the surface thereof toward the deflector or sweepplates may have thereonequally spaced radially extending coatings34 of amaterial, such as graphite, which does not emit secondary electrons. Theremaining wedge-shaped or substantially sectoral portions 35 of thissurface constitute secondary electron emissive targets.

- Alternatively, the targets 35 may be coatings of a secondary electronemissivematerial, such .as matrices including silver oxide, caesium,oxide and some free caesium.

An annular or cylindrical collector electrode 36 is disposed injuxtaposition to the targets 35 and is supported coaxial with thedisc32.by a leadingin conductor 3'! sealed in the stem l2.

Disposed in circular formation about an. axis coincident with that ofthe electrode 32 and I collector electrode 33 area plurality of curvedtrapezoidal deflector plates 38, each of .Whichis supported opposite acorresponding one .of the targets 35, as by a leading-in conductor 39sealed in the stem [2, and is slightly inclined, as illustrated in Fig.5, with respect to the. stem..l2.

shown in Fig. 5, the sweep or deflector plates are maintained at apositive potential, for example, of the order of three hundred volts, byconnections from the mid-points of the secondary windings of thetransformers 48 to the battery 45 so that these plates serve as a secondanode. If desired, the deflector or sweep plates may be biased at apotential higher than that upon the anode 26, for example, at apotential of the order of three times the potential on anode 26.

The target electrode 32, the shield electrode 40 and the deflectorplates have applied thereto the same potential as the sweep or deflectorplates 28 and 29 and the collector electrode 36 is maintained at apositive potential, for example, of the order of fifty volts, withrespect to the target electrode, as by a battery 49 in series with aresistance 50.

Individual signal channels 5|, for example, telephone lines, areconnected between the shield electrode 4.0 and the deflector plates 38as through The deflector plates 38 are encompassed by a one another.

During operation of the electronic commutator, the heater filament I4 isenergizedas bya battery 15, and the concentrating electrode ismaintained at a suitable potential, positive .or

negative, with respect to the cathode as by a.

battery 46. The anode '23 is maintained ,at a high positivepotential,for example of the order of six hundred volts, with respect tothecathode as by a battery 43. The deflector or sweep plates 28and 29 haveapplied thereto a high frequency for example, of .the order of sixtransformers .52.

.The battery 49 and resistance Snare bridged across the input circuit 53of an amplifier,

a suitable blocking condenser .55 being provided as shown. The outputcircuit of the amplifier 54 maybe connected .toa common transmissionchannel.

When the electronic commutator is operated, the electrons emanating fromthe cathode l5 are concentrated into a beam focussed upon thetargetelectrode 32, the beam being rotated at. high frequency by thefield produced by the deflector or sweep plates .28 and, 29 so that itimpinges upon the targets 35 in succession. The impinging electronscause the emission of secondary electrons and, consequently, a currentwill flow from each of the targets 35 to thecollectorelectrode 36. Eachsecondary electron current may be modulated in accordance with thesignal from the corresponding individual signal channel through theactionof the corresponding deflector plate .38. That is to say,eachdeflector plate will deflect the electron beam radiallysubstantially along an axis such as X-TX shown for onetarget 35 in Fig.2. Hence, ,the time of travelof the electron beam along each target andthe area of .the target energized will be varied in accordancewith thepotentials of the deflector-plates and the .currentsto the collectorelectrodewill correspond to the individual signals.

Acomplex current, it will .be apparent, composed of the severalmodulated currents .will flow through. thev common resistance .50 and.corresponding variationsflwill be producediinthe potential of the gridorcontrol electrode of the amplifier 54. Hence, the output oftheamplifierwillbe, a multiplexed signal having, componentscorresponding to the severalindividual signals.

The multiplexed signal may .be transmitted over a common transmissionchannelto ,areceiving distributor and thereanalyzedasde- .scribed in theapplication Serial No.;255,89'7,. fi led February 11, o 1939, ofFrankGray.

Although the electron beam has been, described as rotated by anelectrostatic field, it may be rotated also by a magnetic fieldproducedforexample,.by external coils. It wil1 be,understo0d also that,although. a specific embodiment of this invention has been shown anddescribed, various modificationsmay be made therein withoutdepartingfrom the scope and spirit of this inven- ,tion as,,definedinntheappended c aim .What; is claimed is:

1- Signal translating apparatus comprising means for producing anelectron beam, a plurality of similar, secondary electron emissivetargets each target being of varying width from the beam axis outwardly,a single collector electrode in cooperative relation with all of saidtargets, means for deflecting said electron beamto impinge upon saidtargets in sequence, and means for controlling the secondary electroncurrent from each of said targets including means for deflecting theelectron beam in directions substantially normal to the width of saidtargets.

2. Signal translating apparatus comprising means for producing anelectron beam, a plurality of similar, secondary electron emissivetargets, each target being of varying width from the beam axisoutwardly, a collector electrode in cooperative relation with saidtargets, means for deflecting said electron beam to impinge upon saidtargets in sequence, and means for controlling the secondary electroncurrent from each of said targets including means for deflecting theelectron beam in directions substantially normal to the width of saidtargets, said targets being wedgeshaped and mounted in circularformation about an axis coincident with the longitudinal axis of saidcollector electrode.

3. Signal translating apparatus comprising means for producing anelectron beam, a plurality of similar secondary electron emissivetargets, each target being of varying width from the beam axisoutwardly, a collector electrode in cooperative relation with saidtargets, means for deflecting said electron beam to impinge upon saidtargets in sequence, and means for controlling the secondary electroncurrent from each of said targets including means for deflecting theelectron beam in directions substantially normal to the width of saidtargets, said controlling means comprising a plurality of deflectingplates, one for each of said targets, each deflecting plate being inalignment with a corresponding one of said targets.

4. Signal translating apparatus comprising a collector electrode, aplurality of secondary electron emissive targets mounted in a circularboundary coaxial with said collector electrode, means for producing anelectron beam, means for rotating said beam so that it impinges uponsaid targets in succession, each target varying in dimension normal tothe direction of the trace of said beam thereon, means for varyingindividually the area of each target impinged upon by said beamincluding means for deflecting said beam along radii of said circularboundary.

5. Signal translating apparatus comprising a collector electrode, aplurality of secondary electron emissive targets mounted in a circularboundary coaxial with said collector electrode, means for producing anelectron beam, means for rotating said beam so that it impinges uponsaid targets in succession, each target varying in dimension normal tothe direction of the trace of said beam thereon, and means for varyingthe area of each target impinged upon by said beam including means fordeflecting said beam along radii of said circular boundary, saiddeflecting means comprising a plurality of deflecting electrodes mountedin a boundary coaxial with said collector electrode, each of saiddeflecting electrodes being in cooperative relation with a correspondingone of said targets.

6. Signal translating apparatus comprising a collector electrode, aplurality of secondary electron emissive targets mounted in a circularboundary coaxial with said collector electrode, means for producing anelectron beam, means for rotating said beam so that it impinges uponsaid targets in succession, each target varying in dimension normal tothe direction of the trace of said beam thereon, means for varying thearea of each target impinged upon by said beam including means fordeflecting said beam along radii of said circular boundary, said targetsbeing radially extending wedge-shaped portions of an annular member, andnon-emissive coatings upon the portions of said member intermediate thewedge-shaped portions.

'7. Signal translating apparatus comprising a collector electrode, aplurality of secondary electron emissive targets mounted in a circlecoaxial with said collector electrode, means for producing a rotatingelectron beam impinging upon said targets in succession, the dimensionof each target in the direction of the trace of the beam thereon varyingoutwardly with respect to the center of said circle, a plurality of beamdeflecting electrodes, each in alignment with a corresponding one ofsaid targets, and. shield members between successive deflectingelectrodes.

8. Signal translating apparatus in accordance with claim 7 comprising ashield electrode encompassing said deflecting electrodes.

9. Signal translating apparatus comprising a collector electrode, aplurality of secondary electron emissive targets mounted in and alongradii of a circular boundary coaxial with said collector electrode, eachof said targets varying in dimension normal to the corresponding radiusof said' boundary, a plurality of deflector plates, one for each of saidtargets and in alignment therewith, said plates being mounted in aboundary coaxial with said collector electrode, a hollow electrodeencompassing said deflector plates, coaxial with the boundary thereof,and defining a substantialiy annular passageway therewith, means forproducing an electron beam, and means for rotating said beam in saidpassageway to impinge upon said targets in succession.

10. Signal translating apparatus in accordance with claim 9 wherein saidhollow electrode comprises a base having therein a plurality ofapertures, one for each of said targets, each aperture being inalignment with the corresponding target.

11. Signal translating apparatus in accordance with claim 9 comprisingshields for screening said deflector plates from one another.

12. Signal translating apparatus in accordance with claim 9 comprising aplurality of radially extending vanes integral with said hollowelectrode, each vane projecting between two successive deflector plates.

FRANK GRAY. JOHN B. JOHNSON.

